/Engine/Source/Runtime/Engine/Classes/Animation/AttributeBlendOperator.h
Invoked when an attribute container is supposed to be made additive with regards to container B
virtual void ConvertToAdditive ( const [FAttributeBlendData](API\Runtime\Engine\Animation\FAttributeBlendData) & BlendData, [FStackAttributeContainer](API\Runtime\Engine\Animation\FStackAttributeContainer) * OutAdditiveAttributes ) const